/*
* $Id: StrutsTypeConverter.java 651946 2008-04-27 13:41:38Z apetrelli $
*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing,
* software distributed under the License is distributed on an
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
* KIND, either express or implied. See the License for the
* specific language governing permissions and limitations
* under the License.
*/
package org.apache.struts2.util;
import java.util.Map;
import com.opensymphony.xwork2.conversion.impl.DefaultTypeConverter;
/**
* <!-- START SNIPPET: javadoc -->
*
* Base class for type converters used in Struts. This class provides two abstract methods that are used to convert
* both to and from strings -- the critical functionality that is core to Struts's type coversion system.
*
* <p/> Type converters do not have to use this class. It is merely a helper base class, although it is recommended that
* you use this class as it provides the common type conversion contract required for all web-based type conversion.
*
* <p/> There's a hook (fall back method) called <code>performFallbackConversion</code> of which
* could be used to perform some fallback conversion if <code>convertValue</code> method of this
* failed. By default it just ask its super class (Ognl's DefaultTypeConverter) to do the conversion.
*
* <p/> To allow the framework to recognize that a conversion error has occurred, throw an XWorkException or
* preferable a TypeConversionException.
*
* <!-- END SNIPPET: javadoc -->
*
*/
public abstract class StrutsTypeConverter extends DefaultTypeConverter {
public Object convertValue(Map context, Object o, Class toClass) {
if (toClass.equals(String.class)) {
return convertToString(context, o);
} else if (o instanceof String[]) {
return convertFromString(context, (String[]) o, toClass);
} else if (o instanceof String) {
return convertFromString(context, new String[]{(String) o}, toClass);
} else {
return performFallbackConversion(context, o, toClass);
}
}
/**
* Hook to perform a fallback conversion if every default options failed. By default
* this will ask Ognl's DefaultTypeConverter (of which this class extends) to
* perform the conversion.
*
* @param context
* @param o
* @param toClass
* @return The fallback conversion
*/
protected Object performFallbackConversion(Map context, Object o, Class toClass) {
return super.convertValue(context, o, toClass);
}
/**
* Converts one or more String values to the specified class.
*
* @param context the action context
* @param values the String values to be converted, such as those submitted from an HTML form
* @param toClass the class to convert to
* @return the converted object
*/
public abstract Object convertFromString(Map context, String[] values, Class toClass);
/**
* Converts the specified object to a String.
*
* @param context the action context
* @param o the object to be converted
* @return the converted String
*/
public abstract String convertToString(Map context, Object o);
}
|